Punching and/or perforating equipments of this type are included in systems for the automatic processing of documents for punching holes and/or executing transversal thin holes or perforations in continuous forms of paper webs. The forms are supplied, in general, downstream of high speed printers or downstream of suitable unwinding devices.
Such treatments are executed for accomplishing documents which an end user can file, through side holes, in more or less standard ring binders and/or for separating the sheets through facilitated torn off of some portions of the paper form. The transversal perforations are also useful for zig-zag folding the forms along corresponding weakening lines and obtaining regular stacks of easy handling.
Off-line special devices are generally provided for executing the holes of documents to be filed in ring or pin binders. Such devices include punch and die mechanisms with linear actuation which work on the sheets previously separated from. the web and suitable stacked.
Punching devices for photocopying machines, comprising couples of rotating punches and dice are also known. The punches and the dice cooperate with the moving copied sheet and are carried by corresponding rollers tangent to the trajectory of the sheet and kinematically connected one another. An edge sensor detects the passage of an edge of the sheet to be punched and a controlled motor puts in rotation the punches-dice couple and punches the holes at given points of the sheet in response to the information of the edge sensor.
These known punching devices are not suitable for executing holes in continuous forms. In fact, the sole leading edge of the paper web does not ensure a sufficient precision in the positions of the punches with respect to all the documents which can be obtained by the paper web.
Perforation equipments with actuating mechanisms synchronous with the movement of advancing of the form are used for the formation of transversal perforations in continuous paper webs. Such equipments comprise rollers with perforation blades and counter-rollers, heavy and bulky, univocally provided for a single perforation pitch. The accomplishment of perforations of different features requires the substitution of some mechanisms with increasing of costs and drawbacks due to the downtimes and the necessity of using qualified personnel.